High performance explosive compositions are long known. It has been a goal for researchers to find new explosive compositions which can be defined as low impact and shock sensitivity and low flammability, nevertheless offer high energy explosive performance. A combination of these properties offers higher survivability when applied in armor modules as well as greater transportation and handling safety, whilst not deteriorating the overall performance, when compared to readily available explosive compositions of similar energetic properties.
One example of low-flammability explosive compositions is disclosed in U.S. Pat. No. 4,861,397 to Hillstrom disclosing a material comprising an explosive in an amount of 41-85%, an additive selected from the group consisting of zinc borate, hexabromobiphenyl molybdenum flame suppressant, triaryl phosphate ester, calcium formate, antimony oxide, ammonium phosphate, aluminum oxide trihydrate, and organophosphorous diols in an amount of 9-41% and a binder component selected from the group consisting of polyurethane, acrylic polymers, phosphate ester-vinyl chloride latexes, cellulose acetate butyrate, vinyl esters, styrene-ethylene butylene block copolymers fluorinated elastomers, and Plaster of Paris rubberized with acrylic latexes in an amount of 6-39%, all of proportions being on a % by weight basis.
U.S. Pat. No. 5,080,735 to Wagner discloses a cap-sensitive flexible explosive composition of reduced flammability comprising a finely divided cap-sensitive explosive in a flame resistant polymeric binder system which comprises a fluorinated elastomer, or mixture of fluorinated elastomers, admixed with from about 10% to about 30% by weight of a compatible flame retardant material, a drip suppressant, and optionally a cross-linking activator whereby the binder system when exposed to heat from an ignition source will crosslink and harden at a rate which is faster than the rate at which the explosive composition will burn. This material is commercially available and is known as LF-2.
The composition disclosed in the '735 patent is concerned, as stated above, with a cap-sensitive composition. The term ‘cap-sensitive’ composition denotes a substance detonable when subjected to ignition by a so-called No. 8 detonator at unconfined substance conditions, i.e. a substance classified in Class 1.1D according to UN Regulations for the Transport of Dangerous Goods.
The explosive composition, provided between plates of a cassette of a reactive armor module, causes the plates to displace as result of detonation, and thus scatter (break) the jet caused by a warhead hitting the reactive armor module. Some major problems associated with reactive armors arise from the use of excessively sensitive and flammable explosive compositions. Excessive flammability can lead to ignition of the explosive even by small or medium caliber threats. In case the explosive composition burns, a potentially dangerous result may ensue e.g. for a vehicle's crew, because burning of the confined explosive composition may cause detonation, creating some serious hazards for personnel in the vicinity of the vehicle. Moreover, burning increases both the visual and thermal signature of the protected vehicle and further, the fire is likely to consume the entire explosive in the particular armor tile and may even spread to adjacent tiles. Obviously, a reactive armor tile in which the explosive composition has burnt, offers no protection against shaped charge threats.
Other explosive compositions are not fully satisfactory and are either too impact sensitive or shock sensitive and thus may burn and/or detonate at some undesired conditions and further may have unsatisfactory physical or mechanical properties, or suffer from difficulties and limitations in their preparation and application.
It is thus the purpose of the present invention to provide an explosive composition of substantially reduced impact/shock sensitivity and low flammability, which composition is classified in Class 1.5D according to UN regulation, i.e. a composition definable as an extremely insensitive detonating substance (EIDS), and the preparation of which is substantially simple.